The invention relates to an auxiliary-voltage source for supplying electric circuits which are at a high potential, and more particularly control, measuring and regulating circuits, for an electron gun which is supplied with a high voltage and comprises a cathode, heatable through a heater circuit, for the generation of an electron beam and is provided with a power supply which is located in the heater circuit and has an alternating-current section, and whose output current is adjustable.
Auxiliary-voltage sources are known to be used for the stated purpose. Auxiliary-voltage sources serve to supply the anode of a regulator tube, for example, or as heater-current supply for that tube, or generally to supply the electronic components of that tube or of the means for determining the actual value of the beam current, etc.
From German Pat. No. 15 65 145, an electron gun with several regulating circuits provided with auxiliary- or reference-voltage sources is known. However, these auxiliary-voltage sources are practically at ground potential, and there is no auxiliary-voltage source that is at a high potential. This prior-art electron gun has no electric circuits for control, measuring and regulating purposes which are at a high potential and therefore does not require the auxiliary voltage which otherwise would be necessary.
From German Pat. No. 24 60 424, an electron gun is known with regulating and control elements that are at a high potential. The patent makes no mention of an auxiliary-voltage supply for these regulating and control elements. In a practical embodiment of the prior-art regulating arrangement, the auxiliary-voltage sources consist of a mains-connected isolation transformer with a secondary winding that is followed by a further transformer having several secondary windings. The outputs of these secondary windings are applied to voltage regulators or connected to the heater circuit for the regulator tubes. This isolation transformer, which is designed for high potential differences of 150 kilovolts and up, for example, must be properly insulated, which makes it heavy, bulky and expensive. A further isolation transformer is required in every case to heat the cathode, and the prior-art arrangement therefore requires at least two isolation transformer. The term "isolation transformer" is applied to transformers which are designed to withstand potential differences of 10 kilovolts and up.
The use of regulating circuits and control elements which are at a high potential is desirable in that it makes it possible to achieve a control response having a particularly short time constant.